Conventionally, various improvements and proposals have been made with respect to pen nibs for writing and brush-like instruments, in an attempt to refine the writing feeling or performance. Nevertheless, each of them has shortcomings, as follows.
[A] A spearhead-like tip for writing or painting brushes is known. A spearhead-like tip includes a bundle of so-called tapered fibers, i.e. synthetic fibers each formed with a sharpened end, and provides characteristics similar to those of natural hair-made writing tips. However, since only the constituent materials in the natural hair-made tips are replaced simply by the synthetic fibers of the spearhead-like tip, those fibers have to be oriented and tied into a bundle one by one when the tips are produced, which results in a low productivity.
[B] A pen nib for marking pens and the like is known. Such nib can be produced in a relatively simple manner by uniting, by means of adhesive agent, fibers into a bundle which is then formed with a sharpened writing end. On the other hand, such a pen nib does not provide a refined writing feeling because the fibers tend to ravel at the writing end and to become napped at the outer periphery of the tip and, further, because the fibers themselves lack sufficient restoring characteristic.
[C] Another type of pen nib which is known includes a spearhead-shaped cap member formed by molding porous and spongy synthetic resin material with a fiber-made interconnecting core inserted into a bore of the cap member and fixed therein for guiding the ink flow and reinforcing the cap member. In such a pen nib the spongy material provides sufficient pliability and durability to writing pressure. On the other hand however, the tip end of the pen nib made of spongy material tends to tear off and to spring up from the writing surface due to deformation under writing pressure so that a complete contact of the pen nib with the writing surface cannot be achieved. Furthermore, the above-mentioned requirement of the interconnecting core results in complexity of construction and thus increases the number of production steps and hence the production cost of the pen nibs so that the pen nib of this type is not economical.
[D] Still another type of pen nib which is known includes a nib body with slit-like inner capillary channels, formed by extrusion-molding resilient or soft thermoplastic synthetic resin, and shaped to have a sharpened end. Such a pen nib provides an advantage that characters or letters similar to those obtained by writing brushes can be written. However, the writing touch of such a pen nib is relatively harsh, and a satisfactory ink flow characteristic cannot be obtained since the capillary channel is of slit-like structure by which a sufficient amount of ink cannot be retained within the pen point and a so-called drain-back phenomenon tends to occur.
[E] Japanese Utility Model application publication No. 38,691/80 discloses a pen nib wherein fibers are randomly entangled with each other and the surface of and the connections between the fibers are covered or united by elastic resin, such as polyamide-urethane and the like; and the thus obtained nib body is shaped to have a pointed configuration. The pen nib of such a structure has a relatively satisfactory restoring characteristic against writing pressure like the nib consisting of spongy material as mentioned in paragraph [C] above. However, such a pen nib is extremely weak in tensile and bending stresses resulting from scratchy friction by which the tip end tends to be twisted or torn off; therefore, a practically serviceable pen nib with satisfactory properties cannot be attained.